1. Field of the Invention
This application relates to surgical systems and assemblies that include an access device for minimally invasive surgery, and in particular relates to systems and devices that provide access to a surgical location, e.g. adjacent a spine, for one or more instruments to perform a procedure at the surgical location.
2. Description of the Related Art
Spine surgery presents significant difficulties to the physician attempting to reduce chronic back pain or correct spinal deformities without introducing additional trauma due to the spine surgery itself. In order to access the vertebrae to perform spinal procedures, the physician typically makes large incisions and cuts or strips muscle tissue surrounding the spine. In addition, care must be taken not to injure nerve tissue in the area. Consequently, traditional spine surgery carries high risks of scarring, pain, significant blood loss, and extended recovery times.
Apparatuses for performing minimally invasive techniques have been proposed to reduce the trauma of spine surgery by reducing the size of the incision and the degree of muscle stripping in order to access the vertebrae. One such apparatus provides a constant diameter cannula that is made narrow in order to provide a small entry profile. As a result, the cannula provides minimal space for the physician to observe the anatomy and manipulate surgical instruments in order to perform the required procedures. For example, a narrow cannula is typically insufficient to perform one level spinal fixation procedures, which sometimes involves visualization of two vertebrae and introduction of screws, rods, and other large spinal fixation devices.